Background

In the past, obesity has been seen as a problem of adults, becoming more prevalent with advancing age. Fat children have been recognised in literature with Charles Dickens' portrayal of the fat boy in The Pickwick Papers, and Billy Bunter in the 20th century. They were notable because fat children were uncommon.

Now obesity is no longer rare in children and the prevalence is increasing at an alarming rate. Pathological processes (see 'Complications' below) start early in life and are accelerated by obesity. See also separate articles Obesity in Adults and Bariatric Surgery.

Epidemiology^[1]

• Globally, the number of overweight children under the age of five was estimated in 2010 to be more than 42 million.^[2]
• The greatest annual increases in obesity of school-aged children since 1970 have occurred in North America and Western Europe. However, 75% of overweight and obese children live in low- and middle-income countries.^[3]
• Obesity figures in England have more than tripled over a period of 25 years. The most recent health survey in England (2010) has shown that 30.3% of children (aged 2-15) were overweight or obese. 16% of all children were obese.^[4]
• Most recent trends suggest that the rising trend in obesity may be flattening out. In 2011, the number of children aged 2-15 increased by only 0.3% and the number who were overweight actually dropped by 1%.^[4]

Causes

Obesity is basically caused by an imbalance between energy input and expenditure.^[3] There are numerous factors that are thought to contribute to this trend. A few will be considered here. It is worth noting that studies investigating the role of diet or activity are generally small and include diverse methods of risk factor measurement.

Dietary habits

There is a growing cohort of children who develop bad eating habits and a taste for junk food that is high in fat and fast carbohydrates. One study found that whilst consumption of fast food was linked to obesity in 13-15 year-olds, public health interventions that placed restrictions on the location of fast food outlets did not uniformly decrease consumption.^[5]

Exercise

Reduction of physical exercise in the absence of dietary modification contributes to weight gain. Compulsory sport is in decline, although studies suggest that school-based activity programmes aimed to promote physical exercise actually have little impact on children's body mass indices (BMIs).^[6] Long periods in front of the television or playing on the games console also contribute to the increasingly sedentary lifestyle.^[3]

Sleep

Sleep deprivation has been suggested as a contributory factor, although a review of the literature concerning adolescents queried the methodology of many studies.^[7] A possible trend of children going to bed later may be, in part, responsible. Lack of physical exercise may also lead to poor sleep.^[8] Two hormones, leptin and ghrelin, may be important. Leptin is released by fat cells to tell the brain that fat stores are adequate and ghrelin is released by the stomach, as a signal of hunger. In people with too little sleep, leptin levels are low and ghrelin levels high. Both these would encourage an individual to eat more.^[9]

Genetic contribution

Studies suggest that obese children are likely to have obese parents. Current thinking is that this is a result of children with a genetic predisposition to obesity living in an obesogenic environment.^[10] For a fuller discussion, see separate article Obesity in Adults.

Socio-economic situation

A systematic review of countries in the European Union found evidence of a link between obesity and overweight in children and the socio-economic status of the parents, particularly the mother. Furthermore, the prevalence of childhood overweight is linked to the respective country's income inequality or relative poverty.^[11]

New research conducted at Leeds Metropolitan University has, however, raised an interesting slant on the conventional view. The study, which involved a sample of more than 13,000 Leeds schoolchildren, concluded that children living in middle-affluent areas had the greatest probability of being obese. The study postulated that this group was most likely to indulge in 'snacking' between meals.^[12]

Other risk factors

• High birth weight.^[3]
• Timing or rate of maturation.
• Other behavioural or psychological factors.
• Physical conditions such as endocrine causes (rare):^[13]
  • Hypothyroidism - especially Down's syndrome.
  • Cushing's syndrome - look for truncal obesity, hypertension, hirsutism.
  • Growth hormone deficiency - there may be weight gain with delayed puberty.
  • Muscular dystrophy and other causes of immobility.
  • Polycystic ovarian syndrome.
  • Hypothalamic damage.
  • Spina bifida.
  • Genetic syndromes associated with hypogonadism.

Raising the issue^[1]

It can be a delicate issue to raise with a parent and this may mark the (good or bad) start to a long therapeutic period. The issue may be raised:

• If the family expresses concern about the child's weight. Try: "We can measure [child's] weight and see if he or she is overweight for his or her age."
• If the child has weight-related comorbidities. Try: "[Condition] can sometimes be related to a child's weight. I think we should check [child's] weight."
• If the child is visibly overweight. Try: "I see more children these days who are a little overweight. Could we check [child's] weight?"

This may be the first time that weight has been raised with the family. It is a time to be reassuring and supportive. "By taking action now, we have a chance to improve [child's] health in the future."

Diagnosis

Any gold standard for diagnosing obesity would be based on body fat content. Adiposity can be directly measured (eg, densitometry, scanning using dual-energy X-ray absorptiometry) and indirectly (anthropomorphic measurements, bio-electrical impedance and air displacement plethysmography).^[3] This is not practical in primary care. In adults, BMI is often used. The problem with this approach is that it takes no account of factors which have a marked effect on growth in childhood, such as age, gender, puberty and race/ethnicity.^[14] As a rule of thumb, in children a BMI of 20 is significantly overweight and the younger the child, the more this is so.

• BMI per se is not generally a suitable way to assess obesity in children, although it can be used provided that it is moderated by use of adapted charts. The UK90 charts^[15] have been overtaken for use in children aged 2 weeks to 4 years by charts which incorporate data from the World Health Organization (known as the UK-WHO charts)^[16] or the like, to be used in children over 2 years old. In this case, a child with a BMI over the 91st BMI percentile is said to be overweight and a child over the 98th BMI percentile is considered to be obese. These precise figures do vary slightly from one publication to the next.
• In infants between 2 weeks and 24 months old, the 2006 WHO child growth standards for infants and children are used.^[3]
• The value of waist circumference in children is unknown and so measuring it is not recommended.
• Overweight children tend to be tall but centile charts may show that a child is on the 75th centile for height and the 97th centile for weight. This much higher centile for weight than for height suggests obesity. If an overweight child is not tall, refer to a paediatrician.
• In the separate article Centile Charts and Assessing Growth, the problem of diagnosing childhood obesity is discussed more fully.

Parents can be remarkably obtuse in noting that a child is overweight^[17] and charts may be needed to drive the message home. "Puppy fat" is a common excuse or assertions that "his or her glands are the problem." Endocrine causes for childhood obesity are rare. It is worth stressing that obesity is a clinical term with health implications rather than just the way somebody looks.^[18]

Further evaluation

• Explore why help is being requested; is it the child or the family or are there comorbid problems? The child may have been flagged up during the course of the National Child Measurement Programme.^[1][17]
• Perform a physical examination, looking for features of physical causes (see 'Other risk factors', above).
• If acceptable to the child, evaluate pubertal development.
• Height and weight should be in light clothing with no shoes.
• Test urine for protein and glucose. Ideally, check blood pressure but the cuff needs to be suitably sized.
• The National Institute for Health and Clinical Excellence (NICE) recommends tailored clinical intervention if a child's BMI (adjusted for age and sex) is at the 91st centile or above and that assessment for comorbidities should be considered if their BMI is at the 98th centile or above, using 1990 UK reference charts.^[18]

Management

Overweight children and adolescents can be managed in primary care if there is a positive attitude to weight management.

General points^[1][14][18]

• Rapid changes in BMI occur during normal growth; there is a great potential for reducing overweight in children and adolescents.
• Unless the child is seriously overweight or has significant comorbidities, be led by the child's/parent's wishes.
• As children are still growing, the aim is often not weight loss but weight maintenance or even a reduction in the rate of gain of weight.
• Apart from the basic principle that energy intake should be reduced and energy output in the form of physical activity increased, there is little in the way of evidence to support any particular preventive approach. NICE recommends that school, family and societal interventions should be considered in the management and prevention of obesity in children. This may include involving parents in weight loss programmes.
• The suggestion that inadequate sleep in children may aggravate obesity has been noted above. Ensuring adequate sleep may be important.
• Beware of potential underlying psychological factors. There may be 'comfort eating' or even clinical depression that needs treatment.
• Overweight adults need caring, compassionate and empathetic attention. This is even more important in children. Praise success at every occasion, however small.

Diet and exercise

The primary aims of management are dietary modification and the initiation of exercise. Losing weight without exercise is very difficult but the obese child may find it very tough taking exercise up initially.

Diet

• NICE does not recommend using a dietary approach alone.^[18]
• It may be helpful to keep a food diary (assists cognitive approach). Do not forget snacks and drinks.
• It is very unpleasant being hungry and, rather than just cutting back on all food, it may be easier to move to a diet with less fat and more fibre in it.
• As with adults, herbal and 'natural' wonders are also to be avoided, as are diets promoted by 'celebrities'.
• There is some evidence that dieting is more effective when calorie counting is employed. Very low-calorie diets have shown promise but more research is needed.^[14]
• There may be occasions where there is benefit in referral to a dietician, particularly where there is a large amount of weight to be lost and caloric cut has to be balanced by adequate nutrition for ongoing developmental needs.
• This is not easy for the patient and it is important to be positive and reinforcing.

Exercise

• The value of exercise is more than just the calories expended in the session. It tends to increase basal metabolic rate and, after vigorous exercise, metabolism is stimulated for the subsequent 36 hours. It also helps people to feel good about themselves.
• Overweight children often shun exercise because of poor mobility, ready fatigue and "being no good at games". It is important to discuss the options to find something appropriate and sustainable. They may be less disadvantaged at swimming, for example, but the attire shows every bulge.
• The age and aptitudes of the individual must be taken into account. It must be something that the individual will enjoy or he or she will not persevere. This is very important, as the ethos of exercise is not just for the duration of weight loss but for life.
• NICE recommends a total of 60 minutes of at least moderate exercise each day (in one session, or more, shorter sessions lasting a minimum of 10 minutes).
• Exercise need not always be 'formal' - walking, using stairs, cycling and active play all count.
• It is very helpful to involve all the family in development of an active lifestyle.^[19] 

Drugs

The drug management of obesity has been more fully discussed in the separate article Obesity in Adults.

• Drug treatment is not usually recommended for children. Orlistat does not have market authorisation for use in children. A Cochrane review supports the use of orlistat in adolescents over the age of 12 as an adjunct to lifestyle changes, once the potential for adverse effects has been considered.^[20] Pharmacists will not issue over-the-counter orlistat to individuals under 18 years of age.^[21]
• In exceptional cases, where there are physical comorbidities (such as orthopaedic problems or sleep apnoea) or severe psychological comorbidities, there may be a role for drug treatment after dietary, exercise and behavioural programmes have been started and evaluated.^[22]
• NICE does not recommend the use of these drugs in children aged less than 12.
• Treatment should be initiated in a specialist paediatric setting, by multidisciplinary teams with experience of prescribing in this age group. It may be continued in primary care, if local circumstances and/or licensing allow.
• Regular monitoring of physical parameters, psychological factors, behaviour, diet and exercise should be part of the treatment package.
• Treatment regimes should not exceed 6-12 months.^[22]

It is worth noting that there are a number of drugs prescribed for children and adolescents that aggravate weight gain and the risks and benefits should always be considered. They include:^[23]

• Antidepressants including mirtazapine, paroxetine, imipramine.
• Anticonvulsants, particularly sodium valproate, gabapentin, vigabatrin.
• Antipsychotics, especially the atypical antipsychotics aripiprazole, chlorpromazine, clozapine, olanzapine, pimozide, quetiapine, and risperidone.
• Corticosteroids.

Surgery^[18]

Bariatric surgery is limited to the severely obese who are refractory to other management. In young people, it is generally not recommended but may be considered in exceptional circumstances if:

• Physiological maturity has been reached, or almost reached.
• The BMI is >40 or if it is between 35 and 40 with significant comorbidities.
• All appropriate non-surgical measures have failed to produce adequate results over six months.
• They are receiving intensive specialist assessment.
• They are fit for anaesthesia and surgery.

Bariatric surgery is associated with larger decreases in BMI and greater improvements of some metabolic markers but it is associated with considerable risks^[22] See separate article Bariatric Surgery for more information.

Cognitive approach

This is important and should accompany all the other approaches described above. It is as important in helping the individual understand the problem as it is to help them through treatment. Cognitive approaches seem to work best in pre-pubertal children.^[24] See separate article Cognitive and Behavioural Therapies which discusses behaviour modification.

Follow-up

As with any chronic disease, follow-up must be arranged. This implies interest in the patient's progress. A fortnight to a month would be appropriate at first, with intervals getting longer with time; however, treat it as a chronic disease. The practice may have a nurse-run weight control clinic.

The achievement of a target weight is not the end of the process. Obesity is a chronic disease and needs to be managed throughout the person's life, as relapse is common. 'Yo-yo dieting' with weight going up and down is undesirable and unhealthy.

Referral

Before referral to secondary care, consider referral to community-based treatment programmes such as MEND (mind, exercise, nutrition ... do it!) - the only programme provided nationwide in the UK.^[25] It runs various age-appropriate courses. Consider referral to a paediatrician if:^[26]

• There is serious morbidity related to the weight.
• The height is below the 9th centile, the child is unexpectedly short for the family or if there is a slowed growth velocity.
• There is precocious or delayed puberty (ie younger than 8 or older than 13 in girls and 15 in boys).
• There is a significant learning disability.
• There are symptoms/signs suggestive of an endocrine or genetic problem.
• There is severe or progressive obesity before the age of 2.
• You have other significant concerns.

Complications

These include:^[1]

• Insulin resistance and type 2 diabetes - maturity onset diabetes of the young (MODY).
• Breathing problems - eg, sleep apnoea and asthma.
• Orthopaedic conditions.
• Raised liver enzymes - indicative of non-alcoholic fatty liver disease.^[3]
• Psychosocial morbidity.^[17]
• Increased likelihood of obesity in adulthood.
• Vitamin D and iron deficiency.^[14] 

There are then problems if these children carry their obesity into adulthood.^[17] There may be an increased future risk of impaired fertility, some cancers, early cardiovascular disease, dyslipidaemia and hypertension. One study reported that retinol binding protein 4, a biochemical marker for comorbidity in adult obesity, could also be found in children.^[27] Another reported that two thirds of severely obese children had cardiovascular risk factors.^[28]

Prognosis

Studies suggest that childhood obesity and adolescent obesity are linked to earlier puberty and menarche in girls, type 2 diabetes, increased incidence of the metabolic syndrome in youth and adults and obesity in adulthood. These changes are associated with cardiovascular disease as well as with several cancers in adults. The underlying mechanisms are thought to be insulin resistance and production of inflammatory cytokines.^[29]

One study found that women who were obese as adolescents consequently grew up to have lower education, income and likelihood of marriage compared with their thinner counterparts. Another reported a link between lower BMI and lower socio-economic status. This relationship was indirect but it has been suggested that higher socio-economic status was associated with access to a healthier diet and organised physical activity.^[30]

Screening^[3]

Currently, the UK National Screening Committee's policy is that there is not enough evidence available to recommend screening children for obesity, as few obesity prevention interventions have been shown to be effective in children.^[31] The policy is due for review this year or next year. However, longitudinal observational studies in children have suggested that opportunistic monitoring of growth charts after 2 years of age may be beneficial. In 2005, an annual National Child Measurement Programme was introduced in England for surveillance (not screening) of two school year groups: reception and year 6. This information is collated by local NHS providers. In some areas, parents of children whose weight lies outside the normal range are sent a letter informing them of the results.^[32]

The future

The English cross-government 'Healthy Weight, Healthy Lives' strategy aimed to reverse the trend in rising childhood obesity so that levels return to those of 2000 by 2020. This led to the introduction of the Change4Life initiative which was launched in 2008. This aimed to improve children's diets and levels of activity.^[33] However, three years later, the Royal College of Physicians issued a report criticising the Government's lack of progress in combating the obesity epidemic. They were particularly critical of the lack of facilities for children, who often do not qualify for medication or bariatric surgery. They have called for less variation in the provision of obesity services and leadership at all levels of NHS provision.^[34] 

The Royal College of Paediatrics and Child Health recently issued a position statement on childhood obesity. This identified many possible initiatives to combat the problem. The salient points were:^[35]

• An increase in training for health professionals.
• Encouraging breast-feeding.
• Extending the free school meals programme.
• Increasing the amount of moderate-intensity exercise undertaken daily by schoolchildren.
• Banning the advertising on television of unhealthy food before the watershed.
• Increasing the tax on unhealthy food.

The use of drugs in children is continually being assessed and may well play an increasing role in the face of the obesity epidemic. One study found that metformin given to children or young people aged 8-18 caused a reduction in BMI and had a beneficial effect on insulin and glucose, alanine aminotransferase (ALT) levels and adiponectin to leptin ratio (ALR - a marker for cardiovascular risk).^[36]